The present invention relates in general to transportation of explosive products and, in particular to, a method and system of packaging explosive products such that the transportation thereof may take place under a favorable shipping classification.
Without limiting the scope of the invention, its background is described in connection with shaped charges for perforating hydrocarbon wells to allow for hydrocarbon production, as an example. Shaped charges are typically used to make hydraulic communication passages, called perforations, in a wellbore drilled into the earth that intersects hydrocarbon formations. The perforations are needed as casing is typically cemented in place within the wellbore thereby hydraulically isolating the various formations penetrated by the wellbore. Once the perforations are formed, hydrocarbon fluids may enter the wellbore from the intersected formation.
The shaped charges typically include a housing, a quantity of high explosive and a liner. The liners typically have a generally conical shape, however, the liners could have other shapes including, but not limited to, a generally parabolic shape. The liners are generally formed by compressing powdered metal, however, other techniques may be used to form the liners such as stamping them from sheet metal. In operation, the perforations are made by detonating the high explosive which causes the liner to form a jet that is ejected from the shaped charge at very high velocity. The jet is able to penetrate the casing, the cement and the formation, thereby forming the perforations.
As hydrocarbon producing wells are drill throughout the world, the shaped charges used to perforate the wellbores must be shipped on a worldwide basis. As stated, the shaped charges used to perforate wellbores are explosive products. Thus, the transportation of such shaped charges is highly regulated. For example, shaped charges must be packaged in approved boxes and shipped according to guidelines promulgated by a competent authority. Depending upon the type of shaped charge and how it is packaged, there are several possible shipping classifications for the transportation of shaped charges.
One of the most favorable shipping classifications for transportation of shaped charges is Compatibility Group S of Division 1.4 as promulgated in the United Nations Recommendations on the Transport of Dangerous Goods, which will be referred to herein as U.N. 1.4S. If a product is assigned a U.N. 1.4S classification, this implies that there is no hazard of a mass detonation among a group of boxes containing explosive articles and that if a single explosive article inadvertently initiated inside a box, then no hazardous effects would emanate from the box. For example, when a product is assigned a U.N. 1.4S classification, this implies that if a first-responder to the accident, such as a firefighter, were within a few feet of a box of explosive articles, then there would be no danger of explosion hazards to the responder while the fire is being fought. In addition, if a product is assigned a U.N. 1.4S classification, this means that the packaged product is judged sufficiently safe for transportation on passenger-carrying aircraft and that packages that have different types of explosive products, for example, shaped charges and detonators, may be shipped together in the same transportation vehicle.
To evaluate whether a package of explosive articles can obtain a U.N. 1.4S classification, it must pass a series of tests described in the United Nations Recommendations on the Transport of Dangerous Goods. Specifically, Test Series 6, which including Tests 6(a), 6(b) and 6(c), is used to determine in which division, amongst Divisions 1.1, 1.2, 1.3 and 1.4 a particular explosive article should be placed. Of particular interest in the transportation of shaped charges is Test 6(a). Test 6(a) is used to determine whether there is a mass explosion of the contents of a single package when one component inside the package is initiated. During the test, the package is confined using boxes or bags that are completely filled with earth or sand and placed as close as possible around the test package to a minimum thickness of confinement in every direction of 0.5 meters or 1.0 meter depending upon the size of the test package.
At least one testing agency outside of the United States, however, has questioned a validity of Test 6(a) due to the confinement of the test package. Instead, this agency has proposed a modification of Test 6(a) which would no longer include the confinement of the test package. While the present packaging methodology used for shaped charges has enabled transportation under the U.N. 1.4S classification, early test results indicate that the present packaging methodology may not be sufficiently robust to pass an unconfined Test 6(a). Therefore, a need has arisen for an improved system and method for packaging shaped charges that will allow such shaped charges, as well as other explosive components, to pass an unconfined Test 6(a) such that the U.N. 1.4S classification will remain achievable.
The present invention disclosed herein comprises a system and a method of packaging explosive products for transportation that will allow such explosive products to pass an unconfined Test 6(a) such that the U.N. 1.4S classification will remain achievable. In the system and method of the present invention, protection against the discharge of fragments created by an inadvertent initiation of an explosive product is provided by placing the explosive products within an expandable bag. In the event of such an initiation, a large volume of gas is rapidly generated which must be initially contained. The expandable bag proves such containment of the expanding gases along with the containment of any fragments. The expandable bag is preferable made from a ballistic cloth or other material capable of initial containment of expanding gases and containment of any fragments.
The expandable bag may be used either alone or in conjunction with shielding panels. Specifically, the present invention may also utilize shielding panels disposed between the explosive products. These shielding panels may be made from wood, aluminum, ballistic cloth or other material that will absorb fragments in the event of an initiation. Additional shielding panels may be placed around the perimeter of the explosive products.
In addition to positioning the explosive products within the expandable bag or within the shielding panel or both, the explosive products are placed within a transportation container to facilitate transportation. This container may typically be a corrugated cardboard box or a wood box.
In one embodiment of the present invention, when the explosive products are shaped charges, additional protection may be provided by disposing a jet spoiler proximate the liner of each of the shaped charges. Preferably, the jet spoilers used in the present invention approximate the size and shape of the cavity within the shaped charge such that the jet spoilers may be disposed within the housing of the shaped charges and in substantial contact with the liner.
Once the jet spoilers are in place, the shaped charges are oriented in a layer configuration such that the jet spoilers positioned within shaped charges in adjacent layers oppose one another. Each layer may include a single shaped charge, a row of shaped charges or an array of shaped charges. In order to assure that all shaped charges to be transported are oriented such that the associated jet spoilers oppose one another, an even number of layers is used. For example, two layers of shaped charges or four layers of shaped charges are common but other even numbers of layers are also suitable.
As such, in the case of the shaped charges, protection may be provided by jet spoilers, the opposing orientation of the shaped charges, interlayer shielding panels, perimeter shielding panels, intralayer shielding panels and the expandable bag, all of which may be placed within a transportation container to facilitate transportation.